Enzyme Names

Some proteins are biological molecules that are capable of catalysing the reaction by lowering their activation energy. It is a highly significant process for surviving. These specialised proteins or biological molecules are termed enzymes. They can catalyse thousands of reactions, and each has a different name. The challenge of remembering their names lead to the naming and classification of enzymes systematically by the IUBM.

Table of Contents:

Naming and Classification of Enzymes
Classification of Enzymes
Oxidoreductase
Transferases
Hydrolases
Lyases
Isomerases
Ligases
Practice Problems
Frequently Asked Questions

Naming and Classification of Enzymes

The enzymes are named according to their classification to ease recalling their names and their recognition. Generally, the enzymes have the suffix -ase attached to their name to ease their identification. The enzyme name generally comprises their substrate and the type of reaction catalysed by them. There are three important features of the nomenclature of the enzymes:

The suffix -ase is generally used for the enzyme, while -it is used for the first newly synthesised enzyme, such as pepsin, insulin and oxygenase, and pepsinogen.
Prefix in the enzyme name identifies the type of reaction, such as pyruvate dehydrogenase, oxidase, hydrolase and others.
The enzyme names can also signify the combined information on the substrate and the type of reaction, such as in urease, DNA polymerase and others.

Naming Convention

IUBM names the enzymes as the EC numbers. The abbreviation for EC is the enzyme classification number. The enzymes are grouped into six categories based on the type of reaction catalysed. Each group has a designated EC number, and the enzymes catalysing that type of reaction fall into the specific group.

The EC number is always separated by a dot. For instance, let us take an enzyme lying in group 1 and catalysing the specific first subclass of reaction. It will have EC number 1.1. Going on further addition of numbers represents sub-sub-class and so on. Each number represents a specific reaction type in each class, sub-class and so on.

Let us take another example of the enzyme with EC number 2.1.4.3. Here, the number 2 indicates a class of enzymes which is transferase. The number 1 states the transfer of a single carbon group. The number 4 signifies catalysis of the reaction involving phosphorus-containing groups or phosphotransferase. The number 3 provides information on the transfer of a phosphoryl group.

Classification of Enzymes

The six categorical division of enzymes is:

EC 1 - Oxidoreductase
EC 2 - Transferase
EC 3 - Hydrolase
EC 4 – Lyase
EC 5 - Isomerase
EC 6 - Ligase

Oxidoreductase

These enzymes catalyse the oxidation and reduction reactions. The electron donation and accepting take place in such reactions where electron acceptors are organic molecules or atoms. The common examples here include oxidases, dehydrogenases and reductases.

Transferases

The reaction here involves the transfer of a group other than hydrogen. It can be an alkyl or phosphate group, amino or carboxylic group or any other. A common example is kinases such as hexokinases in glycolysis, transaminase and others.

Hydrolases

The reactions catalysed by hydrolases include the breaking of bonds along with the addition of water. The most common example is the breaking of the peptide bond (-CONH). Breaking this bond is followed by the addition of water to form a carboxylic group (-COOH) and an amino group (-NH₂). These also break other bonds, such as glycosidic bonds by amylases, lactases and others, and phosphodiester bonds in nucleic acids by nucleases and others.

Lyases

These enzymes are associated with the breakdown of bonds without the removal of water molecules. The lyases either lead to double bond formation or single bond formation. The former category includes synthases, while the latter includes decarboxylases and aldolases. It must be noted that these reactions do not require ATP. Common examples of lyases include fumarase, citrate lyase, pyruvate decarboxylase and others.

Isomerases

The isomerases catalyse isomerisation reactions, including cis and trans isomerisation and racemisation. Isomerase is a molecule with the same chemical formula but a different arrangement of atoms. The isomers are of multiple types as well. A common example of isomerases is phosphoglucomutase which is used in glycolysis to convert glucose-1-phosphate to glucose-6-phosphate.

Ligases

These are the ATP-dependent enzymes that join the two molecules. Their most common usage is seen in ligating the DNA ends during the replication process, and the name is DNA ligase, such as T4 DNA ligase, Taq DNA ligase and others. Besides these, another example is pyruvate carboxylase which acts on the product of glycolysis.

Practice Problems

Q1. What is the full form of IUBM?

a. International Union of Biology and Medicine
b. International Unit of Biochemistry and Molecular Biology
c. Internal Union of Biochemistry and Molecular Biology
d. International Union of Biochemistry and Molecular Biology

Ans. d. International Union of Biochemistry and Molecular Biology

The organisation International Union of Biochemistry and Molecular Biology is concerned with the naming of enzymes.

Q2. What are the constitutive units of enzymes?

a. Glucose
b. Amino acids
c. Carbohydrates
d. RNA
e. Both b and d

Ans. e. Both b and d

Enzymes of proteinaceous nature are made of amino acids, while ribozymes are made of RNA.

Q3. What is the difference between oxidase and oxygenase?

a. Their classification
b. Involvement of oxygen molecule
c. Method of oxygen utilisation
d. None of the above

Ans. c. Method of oxygen utilisation

The enzyme oxidases involve electron transfer from donor or substrate to oxygen, while oxygenases involve the incorporation of oxygen into the substrate.

Frequently Asked Questions

Q1. What are the different sites in the enzymes?
Answer: The enzymes have an active site to bind the substrate and catalyse the reaction. They have an allosteric site that binds the product as an inhibitor. They also have modulatory sites to activate or inhibit the activity of the enzyme.

Q2. Are enzymes important for humans?
Answer: Enzymes catalyse a wide variety of reactions in the body, including carbohydrate breakdown and generation, DNA synthesis, ATP synthesis, oxygen transport, neural signalling, immune reactions and much more. Abnormality in any single enzyme can lead to disorders and lethality.

Q3. What is the difference between enzymes and catalysts?
Answer: Enzymes are biological catalysts or molecules of biological origin. Catalysts, on the other hand, are chemically originated molecules that enhance the speed of reaction. An example of an enzyme is amylase, while the example of a catalyst is nickel.